A team of mechanical engineering students at the University of Pennsylvania have spent the better part of the past year designing and fabricating the ultimate concept bike, which they've called "Alpha." Thanks to rapid prototyping technology, the bike was realized almost entirely at UPenn's engineering school.

Many of the innovations lie in the drivetrain: besides being fully enclosed within the frame, an electronic clutch allows the rider to switch between fixed-gear and freewheel settings. Every aspect of the bike is described in further detail on the dedicated website, but here's a handy rundown of the specs...

The custom handlebars (track drops) are built into the stem to accommodate a LCD screen, not to mention the internal electronics. the bar-end brake lever is wired to drum brake in the front hub, which also houses "a dynamo which generates power for the onboard electronics."

Thus, the rotation of the front wheel "illuminates the integrated rear LEDs and charges two 120 Farad super capacitors." Furthermore, for today's metric-fixated rider, "additional data, which can be used to analyze bike dynamics post-ride, is stored on an SD card that is easily accessible from beneath the handlebars."

Drivetrain

This is where the team demonstrates their engineering prowess:The Switchable Integrated Free-Fixed Transmission uses an electromechanical actuated clutch to switch the bike's configuration between fixed-gear and free-wheeling modes. Metallurgical considerations played a major role in selecting materials for all of the transmission components...

The geometrically complex belt pulleys were made from Stainless Steel using Direct Metal Laser Sintering, a process which allowed us to create otherwise un-machineable parts. Finally, the rear hub incorporates a compact three-speed planetary gear set actuated by a standard push-pull cable.

Carbon-fiber tubes, which house internal cables, are joined by aluminum lugs—all produced in-house using CAD, CAM and CNC-machining (more on that below). The bulbous bottom bracket cluster and fork ends conceal moving parts of the drivetrain, while the belt is hidden inside the right chainstay (as per convention; see video below). The joints were epoxied and cured for five days to ensure structural integrity.

From 30-lb. Aluminum block to bottom bracket...

Manufacturing

Rapid prototyping was paramount to executing the design: "3D printing was used to prototype almost every part before design was finalized and final manufacturing began." For those of you who talk the talk:For final construction, all of Alpha's lugs were CNC machined from billet Aluminum, bead blasted, anodized, and sealed. Many of the transmission components were CNC milled, while the shaft was turned on a CNC lathe and post processed using a collet indexer on a mill.

We made us of a Haas 3-Axis milling machine to achieve the necessary precision for the lugs... We used 80-20 to create a frame that allowed us to prototype the drivetrain with the SWIFT system in it.

While the fork, seatpost, saddle, rims and tires were not fabricated in-house, cyclists will recognize the high-end components (incidentally, I just received my H+Son rims yesterday). Still, this goes way past bike porn:

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Formerly an editor and currently a contributor to Core77 (among other publications), Ray relocated from New York City to the Netherlands in September 2015 to pursue a Master’s in Curating & Writing at the Design Academy Eindhoven. Insatiably curious, he brings a broad interest in popular culture, media, and technology — alongside an abiding passion for art, music, and cycling — to his practice as a journalist and critic.

18 Comments

The design is simply unique.The built up of the construction is nice.Just like the bicycle the ships also have good built ups and design.There are many shipping companies I know have good designs of their ship like the maritime,springdalemaritimeacademy,international maritime etc.I even respect the amount of work and effort put into the construction.The engineering done on it is also very innovative.

As a student, I respect the amount of work that took. But...
It does not make me horny. If it is in fact somewhere beyond bike porn, that place is not a sexy place. Where one gets to when one proceeds beyond porn is in most cases fat and ugly and full of denial. We didn't need to be reminded of the miserable life awaiting members of the adult film industry by this fat ugly bike.
That bottom bracket and fixed gear are an oxymoron. The whole idea of fixed gear bicycles is purity. Pure clean simple function, clean beautiful classic track bike lines. Who would be attracted to this bikes ability to tear your legs off if you hit the wrong switch at speed? If your on a fixed gear bike, you better be ON IT, you are the motor, the drive train, and the BRAKES. You get to know how to ride a fixed gear bike starting from a standstill, and even then your going to get hurt just from the strain on your leg muscles that it requires.
Not just from a design point of view but from an engineering one as well, I just don't understand the point of this projects various features other then to be oddities to catch the eye. The user and the environment it is to fit in do not seem to be considered much. Track bars, on a bike with the transmission of an army tank, and a fixed gear option, on a bike with gears and a freewheel, and on top of that all kinds of cadence and fitness tracking information on a bike that has no other aspects besides the shape of the bars to offer even the casual athletic cyclist.
It is Frankinbike. Or Bikenstien. One of the two. Ether way.

It is good to be practically inventive, especially when you are in the practice and learning stage and congratulations for the ALPHA bike project however, Inventions are to make better products by performance as in strength-stronger than conventional for durability and or more effective at the job than the conventional or both plus, plus, plus talking about which I am challenging one to get in touch with me for a partnership to exploit especially my first spoke wheel set patent financially on a win win relationship at my email walyaula [at] gmail [dot] com. CHEERS!

BSA did a cable-operated fixed/free rear hub during the 1930s. However they did not do it with a 3-speed gear. I am intrigued to know how that is done.
The front hub, with brake and dynamo, is a standard Sturmey-Archer product.
One point that concerns me is the stress transitions where the carbonfibre tubes enter the very rigid lugs.

I'm always interested in how one can integrate the drive-train into a cleaner, self-contained system. I don't see this as final product at all. Just a good exploration. I personally think they should have focused on a commuter-style, especially when it weighs in at a whopping 28 pounds. That's almost twice as much as my carbon road-bike that weighs 16 pounds.
Creating an alternative that's light and functional enough for road use is extremely difficult. The most advanced to date is Shimano's new electronic Dura-Ace 7970 Di2, really the tops out there with flawless mechanical-cable free operation.
I don't see the frame or the handlebars as noteworthy at all, but the drive-train is interesting. We can see some similar industry developments like the Spot/Gates carbon belt drive with 14 speed Rohloff internal rear hub and the Hammerschmidt (internal planetary gear cranks). These are relegated to Mountain and Commuter bikes mainly since they weigh too much for road use.
I'm not sure I can validate any excess mechanics just to gear switch from fixed to free, let alone to do it electronically. Road race bikes are mostly not set up to be fixed. It's kind of combining two unnecessary functions IMHO. Using a Sturmey Archer 3 speed hub is a strange choice for use with a road set up.
Regarding the built in cadence system. I think the add-on systems on the market are more sensible since you can remove them when you don't want it or replace it. Handlebars come in varying widths, so it's much smarter to have the cadence system as an add-on rather than built-in; requiring multiple bar sizes to be manufactured or relegating it to old-tech as soon as the electronics are outdated.
I have a saying: "Just because you can, doesn't mean you should". We have alot of "look what we can do here".
That said, I think if they made a similar electronic shifting set-up for urban use, they'd have a winner on their hands. They should integrate the horn, lighting and GPS too (or iPhone).

As an engineering student, I think it's cool to see what other students are doing in their projects. I think the point of doing a project like this is to force oneself to think through all the aspects of a bike. Perhaps nothing revolutionary was implemented on this bike, but revolutions often come from incremental adaptations which you get by being in the trenches with the problems.

Isn't the impressive point of the bike enclosing the drivetrain? They seem to be moving towards (if not already) merging the bottom bracket, the gearing, the derailleurs, etc. Neither the specialized, trek or felt set out to do that. I don't think they were trying to innovate the lugs. I'm not actually sure why they would try and make it a fixed gear, but comparing it to a flip flop hub is short sighted.

Hello all,
To the negative comments above remember these are students, Have you ever tried to design something and then build it in 16 weeks/one semester? This is a huge undertaking while managing other classes and god forbid a social life in engineering school. These projects are meant to teach not to save the world.
On the notion of the power source in the front hub is there more information on how they did this? I am very interested for a project of my own.
Thank you.

Ray, thanks for the post (gosh...some people here are too cool for school....) also be interesting to also read about what the UPenn students learned about bike design, rapid prototyping, and design process/design thinking in general from this project. i.e.:can they apply what they learned to micro urban transportation solutions ?

Google and find Specialized's Epic Allez from the early 90s and then Schlumpf's drivetrain and buzzkill yourself on the most high-tech bicycle ever made. Then find a "flip-flop hub" that's been around for about a hundred years. Now some grad students learning how to use a 3D printer and doing it with a bike, sure. But c'mon. A monocoque bike with a internal drivetrain maybe slightly more "high tech" and "ever made." Bonus points for doing it in bamboo.

Thanks for reporting on the bike. It's an engineering student project and it's interesting as one. Very high tech and using new tools to push Fabrication technology,etc,etc... To the detractors comments, You are using a designers eye to measure a engineers project. Different motives and skill sets.

Interesting project, but I'm with Turz. How about putting all of that effort, money and engineering talent into something that's actually better than something you can buy for $500. How much drag do those idler pulleys add just so they can route the belt (which looks somewhat skinnier than the current carbon belt drives which don't hold up that well, by the way) through the chainstay...maraging steel bb axle?? would chromoly not be sufficient? ...I just think all of this energy could have been directed to solve an actual problem...

Hi Turz,
Thank you for the comment. I chose to write about "Alpha" because (besides the fact that I personally found it fascinating) I thought our readers would be interested in this project and how it was documented from concept to execution, especially with regard to use of rapid prototyping technology. I'm not sure if there have been examples of this in the past that you have in mind, or maybe I'm just a sucker for CNC-machining and exploded schematics...
I can't speak to the cost or the "point" of the project-- at very least, it's cooler than anything I did in school-- but I agree that the oversized lugs (the seatstay cluster in particular) look strange. Obviously, just because I've never heard of a transmission that shifts between fixed and freewheel doesn't mean it hasn't been done before, so I'd love to learn more about other examples of high-tech bikes. I'm also curious as to which "bicycles in the last 20 years" you are referring to. Any chance you could send (or comment) some links? Maybe some of the designs are worthy of a blog post of their own...
Lastly, the "bike porn" comment was intended as a joke, referring to the fact that they're glamorizing each and every component (and a reference to our previous post on Bertelli, whose designs might look like they're more than 20 years old precisely because they're timeless). As an industrial design blog, we frequently cover bikes-- we recently posted about Jeff Tiedeken and Josh Hadar, not to mention the "Splinter Bike"-- but if you're just looking for images of beautiful bikes, try http://velospace.org. I know Prolly recently posted some photos of Ian's (of Icarus) shop, if you're interested in more traditional framebuilding...
Thank you and I hope you can send some more info my way... in the mean time, I'll be at the New Amsterdam Bike Show this weekend.
-Ray

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